Defect States of Silicon Allotropes for Quantum Information Science

Nontechnical description: The project is focused on the design, synthesis, and structure-properties control of novel forms of silicon, which differ in crystal structure from the conventional silicon used in microelectronic technology. They are being investigated as potentially disruptive materials for quantum information science. The novel structures to be investigated are comprised of 3-dimensional networks of silicon cages and 2-dimensional networks of silicon tunnels that have the unique ability to trap dopant atoms in precise site locations that minimize interaction with the silicon crystalline lattice.

The trapped atoms can act as qubits, the basic element for storing quantum information. These materials could overcome major hurdles being faced with conventional silicon, like challenges with optical coupling and decay of signal due to interactions of qubits with the silicon lattice. Hence, the project could enable optically efficient silicon-based devices, a holy grail of the silicon community.

This research benefits society by providing a new class of materials that would revolutionize several global technological fields including computer chips, lasers, detectors, and telecommunications. The project includes strong and novel education and outreach activities that provide exciting opportunities for K-12 students, undergraduate and graduate students, and underrepresented groups in STEM, including summer workshops and internships, research experiences for undergraduates, and community outreach.

With the project focus on materials development for quantum computing and related applications this is an exceptional opportunity to attract new students to STEM, with innovative design of new hands-on, exportable, activities for a broad range of students and their teachers (elementary, middle, high school), including underrepresented and low income communities in Denver. These activities are designed as both hybrid and in-person. Modules also specifically target the Rocky Mountain Dyslexic Camp for students at all levels.

Technical description: The project is focused on advancing the knowledge on critical properties and controls of spin-defect states that are needed for quantum information science materials. The inherent structure and properties of novel crystalline silicon allotropes provides precise interstitial sites for dopants/qubits to sit, along with the potential for low sensitivity to thermal excitation and long spin lifetimes and decoherence times, coupled with a direct bandgap within the telecommunications wavelength.

The project provides new understanding of spin defects and the research activities could lead to a completely new class of quantum information science materials. The project goals are to design, synthesize, and control the structure-properties of crystalline silicon allotropes with interstitial dopants (inside cages or channels), with controlled defect spin-states with lower sensitivity than diamond Si to thermal excitation and spin relaxation, to mitigate key issues in diamond silicon for revolutionary quantum information science materials.

The project scope includes thin film synthesis and design of silicon allotropes with different crystal structures and dopant types and concentrations/site occupation to enable systematic investigations to understand and control the interstitial spin defect states of the dopants and the relations of structure, optical, electrical, and quantum properties. The project approach and methods include: (i) Synthesis and design of thin films to produce high phase purity allotropes with desired dopants; (ii) Investigation of the structural (X-ray diffraction; confocal Raman; scanning electron microscopy; time of flight secondary ionization mass spectrometry), optical (photoluminescence spectroscopy, absorption), and electrical (conductivity and mobility) property-relations; (iii) Measurement of spin-defect states using continuous-wave electron paramagnetic resonance and nuclear magnetic resonance spectroscopy; (iv) Pulsed electron paramagnetic resonance study of spin coherence.

Revolutionary discoveries from this project are possible because of the research team’s unique expertise in silicon allotrope synthesis/properties, in fundamental defect/dopant science and in solid-state dopant-based quantum information science approaches.

This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.